JohnActon posted:gunrunnerjohn posted:Just got another 5V board with the infamous 330uf cap bulged and the board is indeed dead. I don't know if that's what killed it, but it didn't help, that's for sure.
I think the primary reason for the failures is the 5V board design runs a number of the components right at the limits, the motor drive FET's are one such part. I personally had one die, and I've gotten two others in for repair that died, all for the same reason. Throw a traction tire, jam the power truck, and if you're not lightning quick, the overload smokes the FET. Of course, the funky heatsink they used on those is almost impossible to get back on right without overheating the FET, so out of three, I only managed to fix one of them. There are also several diodes inside the board stack that die, I don't know if that's caused by another failure, or they're the cause of the failure. Since it's very difficult, bordering on impossible, to split the boards to fix them, that's usually a death sentence for the set.
Another case for gluing the traction tires on. I had a Williams loco back in the early 90s burn up a Dallee eunit that had just been installed a month, with just such a traction tire in the gears. Since then I glue them on. It's not 100% but usually they stay on till their disintegrating and if they do come off it's in small enough pieces that they are not likely to jam in the gears. Two ~ three years ago I was changing the tires on a MTH F3 and decided to glue the tires on one truck and not on the other the unglued tires failed in about a year. They did not tear, just stretched, and would not stay on. In my opinion this is the situation most likely to get the tire jammed in the gears. I thought for years about installing a fuse between the motors and driver to limit current draw and it was your suggestion of poly fuses that got me moving to do something about this. I installed them on all my TMCC and DCS conversions in the last six months and working my way back through earlier conversions and mfg original command locos. let me mention this, talgo trains such as Zephers, AeroTrain and UP M-10000 which have a motor truck on each end of the train have a wiring harness most susceptible to melting down when the tail end car jumps the track or splits a switch shorting the center rail pickup to the outer rail on one end of the train. This can cause not only the DCS TMCC boards to fry it can fry the entire wiring harness the length of the train. Why Lionel or Mike would not address this flaw is just a big ?? I bought a new MTH M-10000 several months ago and have not put it on the track yet or until I can figure a strategy on where and what size poly fuses to install. j
Wouldn't fast blow fuses between the power supply and track address the issue of burning up boards? I've been using fast blow automotive blade fuses between the power supply and the track and have yet to fry a TMCC/PS2 board because of a derailment.
